The Wizard and the Prophet: Two Remarkable Scientists and Their Dueling Visions to Shape Tomorrow's World

by Charles C. Mann

Feeling defensive, I asked if she thought the kind of climate change Al Gore was describing wouldn’t be a catastrophe. Sad, sure, she said, in my recollection. But a catastrophe—no. She paused. Oxygen, she said. Now, that was a catastrophe. The oxygen she was referring to was the Great Oxidation Event, which occurred after cyanobacteria evolved photosynthesis. Photosynthetic creatures spread through the oceans, excreting oxygen all the while. The flood of oxygen permanently changed the surface of the earth, the composition of the oceans, and the functioning of the atmosphere. Most scientists believe it made the vast majority of the world’s land and sea uninhabitable for the vast majority of the planet’s living creatures. Margulis called the resultant slaughter an “oxygen holocaust.” Over time, minerals absorbed much of the gas, stabilizing it at about 21 percent of the atmosphere—a good thing, because if the level had risen much more our air would have had so much oxygen that a single spark could have set the planet afire.